Bore sighting fixture



March 13, 1951 P. F. PETERSON some swarms FIXTURE Filed April 22, 1946 Z6 29 za /7 g In! INVEN TOR.

Attorneys Patented Mar. 13, 1951 BORE SIGHTING FIXTURE Paul F. Peterson, Los Angeles, Calif., assignor to North American Aviation, Inc.

Application April 22, 1946, Serial No. 663,802

2 Claims.

" This invention relates to the bore sighting of guns mounted in aircraft or the like. In general, its object is to provide a fixture by which the barrels of machine guns or the like may be properly oriented after initial orientation withoutthe necessity of leveling the plane or using a target located remotely as in conventional sighting procedure.

A specific object of the invention is to pro- "vide an apparatus embodying a miniature tari get adapted to be fixed directly to an airplane l in line with the barrel of a gun previously aligned, so that further sighting of the gun barrel may be accomplished irrespective of the position l or location of the plane.

Another obiect of the invention is to provide a I fixture such as that referred to in the preceding 1, paragraph, embodying means for adjusting the target with reference to the airplane. A still further object is to provide a target having means for accurately gauging a desired amount of adjustment thereof. A still further obiect is to prov vide such a target, having means for gauging adjustment thereof both in elevation and in azimuth.

Other ob ects will become apparent in the ensuing specifications and appended drawings in g which: I I a Fig. 1 is a front ele ation of a target device embodying my invention;

Fig. 2 is a plan view of the same from the under side thereof, parts being broken away and shown in sect on in order to illustrate the construction thereof; i

Fig. 3 is a vertical transversesectional view through a portion of an aircraft wing with a machine gun and mv improved bore sighting apparatus-attached thereto;

Fig 4 is a plan View of a portion of the aircraft wing with a portion of a machine gun and by improved apparatus attached thereto.

As an example of one form in which the invention may be embodied, I have shown in the drawings a bore sighting apparatus particularly adaptable for bore sighting a machine gun 5 that is mounted in the wing 6 of an airplane, with the muzzle'of its barrel 1 spaced from the leading edge 8 of the wing. The machine gun is mounted on a universal pivot 9 intermediate its ends, and near its rear end is provided with mechanism I by means of which it may be adjusted either horizontally or vertically.

initially, the gun is bore sighted by a conventional target metho'd. That is, the plane is leveled in front of a target which is located at a pre-determined distance therefrom, the target is then sighted through the bore of the gun, and

' thegun is adjusted until the line of sight intersects a pre-determined point on the target in accordance with the firing pattern that is to be established. This operation is repeated for each of the guns of the airplane. The gun mounts are locked with the guns in the positions thus de- .termined.

The aircraft isfitted with a blast tube H for each, gun, and a pair of fittings l2 cooperate withthe target device is in any subsequent bore sighting operations. .Each blast tube ll comprises a sleeve into which the muzzle of the gun barrel projects. On either side of the forward ends of the blast tubes fittings l2 are secured to the inner surface of the skin of the wing 6 at the leading edge 8. After the guns have been bore sighted as aforesaid, the pairs of fittings [2 are each jig drilled with a pilot hole l3 adapted to receive the pilot pins l 4 of the target device I5.

5 The target device 15 comprises a frame l6 hav- 7 ing at its ends, bosses H in which are mounted the pins 44, and having a central opening l8.

,"Over the opening I 8 is secured a transparent target window !9 having imprinted thereon a tarlines 2| and horizontal lines 23. and 23 are arranged at 90 degrees to each other get 20 and cross-hair lines including vertical The lines 2| and, extended, would intersect the center of the target 20.

- It by studs 25 which extend through longitudinal slots 2! in the window is and through vertical slots 28 inthe frame [6. Knurled thumb nuts 29 are threaded onto the ends of the studs 26 and engage spring washers 30 which in turn engage the surface of the target window 19. Heads 3| on the other ends of the studs 26 engage the rear side of the frame 16.

By loosening the thumb nuts 29, it becomes possible to slide the target window l9 either vertically or horizontally. A pre-determined vertical setting may be quickly effected by registering the cross-hairs 23 with selected marks on the scales 24, and in a like manner a pre-determined horizontal setting may be effected by registering the vertical cross-hairs 2| with preselected marks on the vertical scales 25. The readings on the scales 24- and 25 may be determined by reference to previously prepared charts. For each of a series of desirable fire patterns, there may be a chart giving the readings from which that fire pattern can be realized by bore sighting the guns of the airplane to the readings given for the respective guns.

The original target bore sighting of the gunsforms the basis for locating the fixture by means of the fittings 12. Thus, a jig having a target identical with is applied to the leading edge of the wing and sighted to determine the position in which the holes l3 shall be drilled, and the position of the target device for this purpose is determined by sighting through a barrel l and lining up the target 20 therewith. Previous to this sighting, the target window [.5 is properly set with reference tothe dial scales 24 and to correspond to the scale readings for the particular pattern of the original bore sighting. This pattern is preferably a normal or a neutral one in which the cross hairs 23 and 2| are lined up with central readings on the scales 24 and 25, such as elevation and "10 azimuth. In this case, the setting 50 would represent the elevation of the guns above the horizontal in order to cause the trajectory of the bullets to pass through the horizontal plane of the gun at a selected distance ahead of the ship (for example, 300 yards), and the setting 10 would indicate the amount of convergence of the guns in order to cause the bullet trajectories to cross each other or converge at the same distance :(300 yards) ahead of the airplane. 'In such bore i'sighting, convergence of the bullet trajectories .at a greater distance ahead of the ship can be effected by adjusting the cross hairs 23 and 2| to scale marks of proper value on the scales 24 .and 25 (e. g. 40 and 15) and convergence at a shorter distance ahead of the ship can be sighting device 32 which, by means of a prism,

reflects the line of sight at a degree angle. This sightin device is simply inserted "into the breach end of the barrel I as indicated in Fig. 3

I and the sighting is done from above.

It is to be understood that the inventionis equally applicable to the bore sighting of guns that are mounted in other structures and in '-parts .ofthe structure of an airplane other than the leading edges of the wings.

I claim as my invention:

1. Apparatus for bore sighting the barrel of a 4 gun adjustably mounted in a fixed part of an airplane comprising a target frame having a central opening and a plurality of pilot pins adapted to be received in pilot openings located in said fixed airplane part in accordance with the previous positioning of said gun by an original target sighting process, said frame also having a dial face provided with vertical and horizontal scale marks, and a transparent target window adjustably secured to said dial face and having thereon a target to be lined up with the bore of said gun through said opening and also having thereon scale marks adapted to be related to the scale marks on said dial face in order to determine a desired position of adjustment of said target with reference to said dial face.

2. Apparatus for bore sighting the barrel of a gun adjustably mounted in a fixed part of an airplane, comprising a target frame having a central opening and having pilot means cooperable with pilot means on said fixed airplane part for orienting said frame in a predetermined position with reference to said part with said opening generally align-ed with the barrel of said gun, said frame also having a dial face provided with scale marks; and a transparent target window adjustably mounted on said dial face and having thereon a target adapted to be sighted through the barrel of said gun and a plurality of scale marks adapted to be related to the scale marks on said dial face to determine a desired position of said target with reference to said dial face and thereby determine-a desired positioning-0f said gun; said target window and frameeach having apair of parallel slots, the slots of one being vertical and the slots of the other being horizontal, and including clamping bolts extending through re spective slots and adapted to clamp said target Window to said dial face in a desired position of adjustment.

PAUL F. PETERSON.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 793,131 Henkes June 27, 1905 803,435 Saegmuller Oct. 31, 1905 1,400,772 Schleth Dec. 20, 1921 1,667,995 Steinle May 1, 1928 2,079,791 Cook May 11, 1937 2,412,017 Taylor et al Dec. 3, 1946 2,516,435 Trimbach et al. July 25, 1950 FOREIGN PATENTS Number Country Date 13,571 Great Britain 190 307.257

Germany Aug. 6,1918 

